U.S. patent number 8,849,079 [Application Number 13/220,534] was granted by the patent office on 2014-09-30 for light diffusing element and light guide for endoscopes equipped with the light diffusing element.
This patent grant is currently assigned to Fujifilm Corporation. The grantee listed for this patent is Tadashi Kasamatsu, Koji Yoshida, Tatsuya Yoshihiro. Invention is credited to Tadashi Kasamatsu, Koji Yoshida, Tatsuya Yoshihiro.
United States Patent |
8,849,079 |
Yoshida , et al. |
September 30, 2014 |
Light diffusing element and light guide for endoscopes equipped
with the light diffusing element
Abstract
A light diffusing element diffuses light output from an output
facet of an optical fiber that enters the light diffusing element
at a first end and outputting the diffused light from a second end.
The light diffusing element is equipped with a semireflective
surface for reflecting a portion of the light, provided at a
predetermined portion of the light diffusing element corresponding
to the core of the output facet. The semireflective surface
intersects at least with the optical axis of the optical fiber.
Thereby, propagation of light in directions away from the optical
axis of the optical fiber can be promoted during the step of
reflecting the portion of the light that enters the light diffusing
element.
Inventors: |
Yoshida; Koji (Kanagawa-ken,
JP), Kasamatsu; Tadashi (Kanagawa-ken, JP),
Yoshihiro; Tatsuya (Kanagawa-ken, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Yoshida; Koji
Kasamatsu; Tadashi
Yoshihiro; Tatsuya |
Kanagawa-ken
Kanagawa-ken
Kanagawa-ken |
N/A
N/A
N/A |
JP
JP
JP |
|
|
Assignee: |
Fujifilm Corporation (Tokyo,
JP)
|
Family
ID: |
45697381 |
Appl.
No.: |
13/220,534 |
Filed: |
August 29, 2011 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20120051693 A1 |
Mar 1, 2012 |
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Foreign Application Priority Data
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Aug 31, 2010 [JP] |
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2010-194940 |
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Current U.S.
Class: |
385/31 |
Current CPC
Class: |
G02B
23/2469 (20130101); G02B 6/0008 (20130101); G02B
5/02 (20130101) |
Current International
Class: |
G02B
6/26 (20060101); G02B 6/42 (20060101) |
Field of
Search: |
;606/17 ;362/574,558
;385/79 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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57-31834 (A) |
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Feb 1982 |
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JP |
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1-185510 (A) |
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Jul 1989 |
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JP |
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2001-166223 |
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Jun 2001 |
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JP |
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2009-297188 (A) |
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Dec 2009 |
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JP |
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Other References
English Translation of JP 57/031834. cited by examiner .
Notice of Grounds for Rejection dated Oct. 15, 2013, with English
translation. cited by applicant.
|
Primary Examiner: Peace; Rhonda
Attorney, Agent or Firm: McGinn IP Law Group, PLLC
Claims
What is claimed is:
1. A light diffusing element, for diffusing light output from an
output facet of an optical fiber that enters the light diffusing
element at a first end and outputting the diffused light from a
second end, comprising: the first end; the second end; and a
semireflective surface for reflecting a portion of the light,
provided at a predetermined portion of the light diffusing element
corresponding to the core of the output facet, the semireflective
surface intersecting at least with the optical axis of the optical
fiber, wherein the semireflective surface is formed by a
semireflective film provided on the predetermined portion of a
diffusion output surface, from which the light is output, the
semireflective surface reflects the portion of the light rearward,
and the semireflective surface is shaped as a protrusion that
protrudes rearward.
2. A light diffusing element as defined in claim 1, wherein: the
semireflective surface is of a conical shape.
3. A light diffusing element as defined in claim 2, wherein: the
semireflective surface is of a polygonal conical shape constituted
by a plurality of surfaces.
4. A light diffusing element as defined in claim 1, further
comprising: a totally reflective film which is coated on a surface
of the light diffusing element, such that the light reflected by
the semireflective surface, is reflected frontward.
5. A light diffusing element as defined in claim 1, further
comprising: a second reflective surface, for reflecting a portion
of the light reflected by the semireflective surface, which
comprises a first reflective surface, frontward.
6. A light guide for an endoscope that diffuses light which is
output from an output facet of an optical fiber and enters the
light guide at a first end and outputs the diffused light from a
second end, comprising: the optical fiber; and a light diffusing
element, the light diffusing element being equipped with a
semireflective surface for reflecting a portion of the light,
provided at a predetermined portion of the light diffusing element
corresponding to the core of the output facet, the semireflective
surface intersecting at least with the optical axis of the optical
fiber, and the semireflective surface being formed by a
semireflective film provided on the predetermined portion of a
diffusion output surface, from which the light is output, the
semireflective surface reflects the portion of the light rearward,
the semireflective surface is shaped as a protrusion that protrudes
rearward.
7. A light guide for an endoscope as defined in Claim 6, wherein:
the semireflective surface is of a conical shape.
8. A light guide for an endoscope as defined in claim 7, wherein:
the semireflective surface is of a polygonal conical shape
constituted by a plurality of surfaces.
9. A light guide for an endoscope as defined in claim 6, further
comprising: a totally reflective film which is coated on a surface
of the light diffusing element, such that the light reflected by
the semireflective surface, is reflected frontward.
10. A light guide for an endoscope as defined in claim 6, further
comprising: a reflective member, for reflecting a portion of the
light reflected by the semireflective surface, frontward.
11. A light guide for an endoscope as defined in claim 6, wherein:
the optical fiber and the light diffusing element are separated by
a predetermined distance.
12. A light guide for an endoscope that diffuses light which is
output from an output facet of an optical fiber and enters the
light guide at a first end and outputs the diffused light from a
second end, comprising: the optical fiber; and a light diffusing
element, the light diffusing element being equipped with a
semireflective surface for reflecting a portion of the light,
provided at a predetermined portion of the light diffusing element
corresponding to the core of the output facet, the semireflective
surface intersecting at least with the optical axis of the optical
fiber, the semireflective surface being formed by a semireflective
film provided on the predetermined portion of a diffusion output
surface, from which the light is output; and the optical fiber has
a tapered portion in the vicinity of the output facet such that the
core of the optical fiber is of a tapered shape that becomes
thinner toward the output facet.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a light diffusing element that
diffuses light output from an optical fiber. The present invention
is also related to a light guide for an endoscope that guides
illumination light to a portion to be observed, equipped with an
optical fiber and the light diffusing element.
2. Description of the Related Art
Endoscope systems for observing tissue within body cavities are
widely known. For example, endoscope systems that obtain visible
images by imaging using white light to illuminate portions to be
observed within body cavities and display the visible images on
screens of monitors are in wide practical use.
Light guides for endoscopes for guiding illumination light into
body cavities are utilized in the aforementioned endoscope systems.
It is possible to utilize laser light sources as light sources for
generating the illumination light.
There are cases that laser beams emitted by laser light sources
will be harmful to human bodies due to their high power densities,
even if the emission amount is low. Accordingly, in the case that a
laser light source is utilized as an illumination light source, it
is preferable to use a laser having the lowest level safety
standard class as possible, from the viewpoint of safety of
operating sites. Commonly, light diffusing elements (referred to as
"light diffusing elements" or "holographic diffusers") that diffuse
light output from optical fibers are provided in the vicinity of
output ends of the optical fibers, in order to decrease the level
of the safety standard class. Light emitting surfaces at output
surfaces of the light diffusing elements diffuse light, and become
a two dimensional light source having a large light emitting area.
In such cases, the light emitting surfaces of the light diffusing
elements being of sizes corresponding to the outputs of laser beams
is a requirement to satisfy safety standards.
Meanwhile, miniaturization of light guides for endoscopes is
advancing, for the reasons of improving operability, endurance, and
the like.
U.S. Pat. No. 6,569,088 discloses a light diffusing element having
a two dimensional shape that maximally utilizes dead space at the
distal end layout of a light guide for an endoscope, in order to
secure a large light emitting surface for the light diffusing
element while miniaturizing the light guide for an endoscope.
However, if the two dimensional size of the light dispersion
element is merely increased to be larger than an output end of an
optical fiber as in U.S. Pat. No. 6,569,088, there is a problem
that light L cannot reach parts of a light diffusing element 93
away from the optical axis of an optical fiber 94, as illustrated
in FIG. 12.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the foregoing
circumstances. It is an object of the present invention to provide
a light diffusing element that diffuses light output from an
optical fiber and a light guide for an endoscope equipped with the
light diffusing element, that enable light to reach portions of the
light diffusing element away from the optical axis of the optical
fiber.
A light diffusing element of the present invention that achieves
the above object is a light diffusing element, for diffusing light
output from the output facet of an optical fiber that enters the
light diffusing element at a first end and outputting the diffused
light from a second end, comprising: the first end; the second end;
and
a semireflective surface for reflecting a portion of the light,
provided at a predetermined portion of the light diffusing element
corresponding to the core of the output facet, the semireflective
surface intersecting at least with the optical axis of the optical
fiber.
In the present specification the term "semireflective surface"
refers to a surface that reflects a portion of light incident
thereon.
The phrase "reflects a portion of light" refers to reflecting a
portion of light that reaches the semireflective surface.
In the light diffusing element of the present invention, it is
preferable for the semireflective surface to reflect the portion of
the light rearward.
In the present specification, the term "rearward" refers to a
direction opposite a "frontward" direction. Here, the term
"frontward" refers to the direction that light output from the
output end of the optical fiber propagates, between the two
directions parallel to the optical axis of the optical fiber. That
is, the term "rearward" refers to the other of the two directions
parallel to the optical axis of the optical fiber.
The phrase "reflect the portion of the light rearward" refers to
reflecting the portion of the light such that wavelength vector
components of the light parallel to the optical axis of the optical
fiber are directed rearward.
It is preferable for the semireflective surface to be shaped as a
protrusion that protrudes rearward. In this case, it is preferable
for the semireflective surface to be of a conical shape. Further,
it is particularly preferable for the semireflective surface to be
of a polygonal conical shape constituted by a plurality of
surfaces.
The semireflective surface may be formed by a semireflective film
provided on the predetermined portion of a dispersion output
surface, from which the light is output. Alternatively, the
semireflective surface may be an interface between materials having
different refractive indices.
It is preferable for the light diffusing element of the present
invention to further comprise:
a totally reflective film which is coated on a surface, such that
the light reflected by the semireflective surface, which is a first
reflective surface, is reflected frontward.
It is preferable for the light diffusing element of the present
invention to further comprise:
a second reflective surface, for reflecting a portion of the light
reflected by the semireflective surface, which is a first
reflective surface, frontward.
In the present specification, the phrase "reflecting a portion of
the light . . . frontward" refers to refers to reflecting the
portion of the light such that wavelength vector components of the
light parallel to the optical axis of the optical fiber are
directed frontward.
In the present specification, the term "totally reflective film"
refers to a film that reflects a large portion of light incident
thereon.
Further, a light guide for an endoscope of the present invention
diffuses light which is output from an output facet of an optical
fiber and enters the light guide at a first end and outputs the
diffused light from a second end, and comprises:
the optical fiber; and
a light diffusing element;
the light diffusing element being equipped with a semireflective
surface for reflecting a portion of the light, provided at a
predetermined portion of the light diffusing element corresponding
to the core of the output facet, the semireflective surface
intersecting at least with the optical axis of the optical
fiber.
In the light guide for an endoscope of the present invention, it is
preferable for the semireflective surface to reflect the portion of
the light rearward.
It is preferable for the semireflective surface to be shaped as a
protrusion that protrudes rearward. In this case, it is more
preferable for the semireflective surface to be of a conical shape.
Further, it is particularly preferable for the semireflective
surface to be of a polygonal conical shape constituted by a
plurality of surfaces.
It is preferable for the light guide for an endoscope of the
present invention to further comprise:
a totally reflective film which is coated on a surface, such that
the light reflected by the semireflective surface, which is a first
reflective surface, is reflected frontward.
It is preferable for the light guide for an endoscope of the
present invention to further comprise:
a reflective member, for reflecting a portion of the light
reflected by the semireflective surface, which is a first
reflective surface, frontward.
In the light guide for an endoscope of the present invention, it is
preferable for the optical fiber has a tapered portion in the
vicinity of the output facet such that the core of the optical
fiber is of a tapered shape that becomes thinner toward the output
facet.
In the light guide for an endoscope of the present invention, it is
preferable for the optical fiber and the light diffusing element to
be separated by a predetermined distance.
The light diffusing element of the present invention and the light
guide for an endoscope equipped with the light diffusing element
have the semireflective surface that reflects a portion of the
light, provided to intersect with at least the optical axis of the
optical fiber. Thereby, propagation of light in directions away
from the optical axis of the optical fiber can be promoted during
the step of reflecting the portion of the light that enters the
light diffusing element. As a result, it becomes possible for light
to reach portions of the light diffusing element away from the
optical axis of the optical fiber, in the light diffusing element
and the light guide for an endoscope equipped with the light
diffusing element.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram that illustrates the outer appearance of an
endoscope system that employs a light guide for an endoscope of the
present invention.
FIG. 2 is a diagram that schematically illustrates the inner
structures of the endoscope system that employs the light guide for
an endoscope of the present invention.
FIG. 3 is a diagram that schematically illustrates the outer
appearance of structures in the case that the tip of an endoscope
probe portion of the present invention is viewed from the
front.
FIG. 4 is a sectional diagram that schematically illustrates a
first embodiment of the light guide for an endoscope of the present
invention.
FIG. 5A is a diagram that schematically illustrates the structure
of a light guide for an endoscope which is designed such that a
semireflective surface formed as a curved surface protrudes
rearward.
FIG. 5B is a diagram that schematically illustrates the structure
of a light guide for an endoscope which is designed such that a
semireflective surface formed as a cone protrudes rearward.
FIG. 6A is a front view that schematically illustrates the
structure of the light diffusing element of FIG. 5B in the case
that the conical semireflective film is formed as a triangular
cone.
FIG. 6B is a diagram that schematically illustrates the structure
of a light guide for an endoscope which is designed such that a
semireflective surface formed as a cone protrudes frontward.
FIG. 7 is a collection of sectional diagrams that schematically
illustrate examples of a second embodiment of the light guide for
an endoscope of the present invention.
FIG. 8 is a collection of sectional diagrams that schematically
illustrate examples of a third embodiment of the light guide for an
endoscope of the present invention.
FIG. 9 is a collection of diagrams that illustrate an example of a
fourth embodiment of the light guide for an endoscope of the
present invention.
FIG. 10 is a collection of sectional diagrams that schematically
illustrate examples of a fifth and a sixth embodiment of the light
guide for an endoscope of the present invention.
FIG. 11 is a sectional diagram that schematically illustrates a
seventh embodiment of the light guide for an endoscope of the
present invention.
FIG. 12 is a sectional diagram that schematically illustrates a
conventional light guide for an endoscope.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the present invention will be described
with reference to the attached drawings. However, the present
invention is not limited to the embodiments to be described below.
Note that the dimensions, scale, etc. of constituent elements in
the drawings may differ from the actual dimensions, scale, etc., in
order to facilitate visual understanding.
[Embodiments of Light Diffusing Element and Light Guide for an
Endoscope Equipped with the Light Diffusing Element]
A light diffusing element according to a first embodiment and a
light guide for an endoscope equipped with the light diffusing
element are utilized in an endoscope system 2 such as that
illustrated in FIG. 1. As illustrated in FIG. 1, the endoscope
system 2 is constituted by: an electronic endoscope 10 for
obtaining images of portions to be observed within the bodies (body
cavities) of subjects; a processing apparatus 11 for generating
endoscope images; and a light source apparatus 12 that supplies
illumination light for illuminating the interiors of the body
cavities. A monitor 20 for displaying the endoscope images is
connected to the processing apparatus 11.
The electronic endoscope 10 is equipped with: a probe portion 13 to
be inserted into body cavities; an operating portion 14 which is
provided at the base end of the probe 13; and a universal cord 15
that extends from the operating portion 14. The probe portion 13 is
constituted by: a long thin flexible tube portion 13a; a bight
portion formed by a plurality of linked bight pieces; and a tip
portion 13c positioned at the distal end of the probe portion 13.
The tip portion 13c is formed by a rigid metal material or the
like, and houses a CCD 30 (refer to FIG. 2) or the like for
obtaining images within the body cavities therein.
The operating portion 14 is equipped with a forceps opening 17, an
angle knob 18, and the like. The forceps opening 17 is linked to a
forceps outlet 27 (refer to FIG. 2) formed in the tip portion 13c.
Treatment implements are inserted through the forceps opening 17,
and caused to protrude into the body cavities through the forceps
outlet 27. The angle knob 18 is connected to the bight portion 13b
via wires provided within the probe portion 13. The bight portion
13b bends to moves in the vertical and horizontal directions by
pushing and pulling the wires by manipulating the angle knob 18.
Thereby, the tip portion 13c can be oriented toward desired
directions within the body cavities.
A connector 19 is provided at the extended end of the universal
cord 15. The connector 19 is a combination type connector
constituted by a communications connector 19a and a light source
connector 19b, and is capable of being removably connected to the
processing apparatus 11 and the light source apparatus 12.
As illustrated in FIG. 2 and FIG. 3, an objective lens 25 that
receives and focuses image light of subjects, a light diffusing
element 33 that outputs diffused illumination light, and the
forceps outlet 27 are provided on the distal end surface of the tip
portion 13c of the electronic endoscope 10. A light guiding optical
system 28 and a prism 29 are provided to the rear of the objective
lens 25. The CCD 30 is provided directly beneath the prism 29, and
the CCD 30 is connected to a circuit board 31. Image light of
subjects which has passed through the light guiding optical system
28 and the prism 29 enters a light receiving surface of the CCD 30.
The CCD 30 outputs image signals based on the image light that
enters the light receiving surface, and inputs the image signals to
the circuit board 31.
The circuit board 31 is connected to a timing/driver circuit 42 and
a digital signal processing circuit 43 (DSP 43) of the processing
apparatus 11 via signal cables 32. The circuit board 31 is equipped
with an analog signal processing circuit (not shown). The analog
signal processing circuit administers a correlated double sampling
process on the image signals input from the CCD 30, to remove reset
noise and amplifier noise. Then, the image signals, from which
noise has been removed, are amplified at a predetermined gain then
converted to digital signals having a predetermined number of bits.
The digital image signals are input to the DSP 43 of the processing
apparatus 11 via the signal cables 32.
The light diffusing element 33 is provided as an illuminating
window for illumination light at the distal end surface of the tip
portion 13c of the electronic endoscope 10. The light diffusing
element 33 of the first embodiment is constituted by a light
transmitting member 37 in which fine scattering particles are
dispersed, a semireflective film 38, and a totally reflective film
39, as illustrated in FIG. 3 and FIG. 4. The light diffusing
element 33 is of a shape that effectively utilizes dead space
within the distal end layout of the light guide for an endoscope,
as illustrated in FIG. 3. Thereby, the light diffusing element 33
is of a larger two dimensional size than an output facet of an
optical fiber 34, which is a light guide for the endoscope, when
viewed in the direction of the optical axis of the optical fiber
34. The light transmitting member 37 is produced by dispersing
polystyrene beads having diameters of 0.5 .mu.m to 10 .mu.m or fine
bubbles within a light transmitting material such as glass or
resin, then performing molding.
The semireflective film 38 forms a semireflective surface S.sub.1
on a light output surface S.sub.0 of the light diffusing element
33. The semireflective film 38 may be a mesh or a dotted film
formed by metal, for example. The semireflective film 38 may be
provided on the surface of the light transmitting member 37 as
illustrated in FIG. 3, or provided within the light transmitting
member 37.
The totally reflective film 39 reflects substantially all of the
light reflected rearward by the semireflective film 38 frontward.
The totally reflective film 39 may be a thickly formed metal film,
for example. The totally reflective film 39 is not necessarily an
indispensable element of the light diffusing element 33. However,
rearwardly reflected light can be more efficiently reflected
frontward by providing the totally reflective film 39. The output
facet of the optical fiber 34, which functions as a light guide, is
provided to face the light diffusing element 33.
The optical fiber 34 penetrates through the probe portion 13, the
operating portion 14, and the interior of the universal cord 15,
and an input facet thereof protrudes out of the end of the light
source connector 19b. When the light source connector 19b is
connected to the light source apparatus 12, the input facet of the
optical fiber 34 is inserted into the interior of the light source
apparatus 12. The illumination light from the light source
apparatus 12 is guided to the tip portion 13c by the optical fiber
34, and irradiated into the interior of the body cavities from the
light diffusing element 33.
The forceps outlet 27 is connected to the forceps opening 17 via a
forceps channel 35. The forceps channel 35 is a cylindrical member
formed by resin, for example. In the case that a diseased site is
to be cut open while under observation with the endoscope, an
electric scalpel 36 (high frequency scalpel), which is a treatment
implement, is inserted into the forceps channel 35 through the
forceps opening 17.
The processing apparatus 11 is equipped with a socket 40 that
engages the communications connector 19a of the universal cord 15.
The socket 40 is assembled into a housing 41 via an insulator (not
shown) to electrically isolate the main body of the processing
apparatus 11 and the connector 19. The housing 41 is grounded to
earth. When the communications connector 19a is engaged with the
socket 40, the CCD 30 is connected to the timing/driver circuit 42
and the DSP 43.
The timing/driver circuit 42 generates control signals (clock
pulses) in response to commands from a CPU 44, and inputs the
control signals to the CCD 30 via the signal cables 32. The control
signals control the timings at which accumulated electric charges
are read out from the CCD 30, the shutter speed of an electronic
shutter of the CCD 30, etc. The DSP 43 administers color
separation, color interpolation, gain correction, white balance
adjustment, gamma correction, etc., on the image signals which are
input via the signal cables 32, to generate image data. The image
data are converted into analog signals by a digital/analog
converter 45, and displayed on the monitor 20 as an endoscope
image.
The light source apparatus 12 is equipped with: a light source 50;
a light source driver 51; a diaphragm adjusting mechanism 52; an
iris driver 53; and a CPU 54 that controls the other components.
The light source 50 is turned ON and OFF according to control
exerted by the light source driver 51, to irradiate illumination
light toward a focusing lens 55 provided forward of the light
source 50. Examples of the light source 50 include: a xenon lamp; a
halogen lamp; an LED (Light Emitting Diode); a fluorescent light
emitting element; and an LD (Laser Diode). The light source 50 is
selected as appropriate according to the type of endoscope image (a
visible image, a fluorescence image, etc.) is to be obtained, that
is, the wavelength of light to be utilized.
The diaphragm adjusting mechanism 52 is provided between the light
source 50 and the focusing lens 55, and adjusts the amount of
illumination light such that the endoscope images obtained by the
CCD 30 are of a substantially uniform brightness. The diaphragm
adjusting mechanism 52 is equipped with: diaphragm wings that
change the diameter (aperture diameter) of an aperture that the
illumination light passes through; and a motor for driving the
diaphragm wings. The iris driver 53 opens and closes the diaphragm
wings of the diaphragm adjusting mechanism 52, to change the area
that the illumination light passes through thereby adjusting the
amount of illumination light that enters the optical fiber 34.
The flexible tube portion 13a of the probe 13 is constituted by: a
flexible helical tube; a net that prevents stretching of the
helical tube; and an outer layer which is a resin coating on the
net. A plurality of the signal cables 32, the forceps channel 35,
and the optical fiber 34 are fed through the interior of the
flexible tube portion 13a parallel to and in proximity to each
other.
Next, the operation of the endoscope system 2 configured as
described above will be described. When the electronic endoscope 10
is connected to the processing apparatus 11, the CCD 30 is
connected to the timing/driver circuit 42 and the DSP 43. When the
power source of the endoscope system 2 is switched ON, the
processing apparatus 11 and the light source apparatus 12 initiate
operations. The light source 50 of the light source apparatus 12 is
turned ON, and illumination light is emitted toward the focusing
lens 55. The illumination light is guided by the focusing lens 55
to the input end of the optical fiber 23, then guided to the tip
portion 13c of the electronic endoscope 10. After the probe portion
13 of the electronic endoscope 10 is inserted within a body cavity
and the illumination light guided by the optical fiber 34
propagates within the light diffusing element 33, the illumination
light is irradiated onto a portion to be observed. As illustrated
in FIG. 4, a portion of light L.sub.0 that propagates through the
light diffusing element 33 is reflected in the rearward direction
by the semireflective surface S.sub.1 formed by the semireflective
film 38. Ideally, the remainder of the light is transmitted through
the semireflective surface S.sub.1. Here, as described previously,
"rearward" refers to a direction opposite a "frontward" direction.
Specifically, in the case that the direction that light output from
the output end of the optical fiber 34 propagates (frontward) in
FIG. 4 is designated as the positive direction along an x axis, the
"rearward" direction is the negative direction along the x axis.
The amount of the portion of the illumination light which is
reflected is not particularly limited, and can be set by the
configuration of the semireflective surface S.sub.1. However, it is
preferable for the semireflective surface S.sub.1 to be designed to
have a reflectance within a range from 35% to 85% (energy
conversion) from the viewpoint of maximizing the light emitting
area of the light diffusing element 33 as a secondary light source.
It is more preferable for the reflectance to be within a range from
40% to 80%, and most preferable for the reflectance to be within a
range from 45% to 75%.
The light which is transmitted through the semireflective surface
S.sub.1 is utilized as illumination light Lt, which illuminates a
region comparatively close to the optical axis C of the optical
fiber 34. Meanwhile, the light which is reflected rearward by the
semireflective surface S.sub.1 is reflected by the totally
reflective film 39, which is coated on the side of the light
diffusing element 33 toward a light input surface thereof. The
light undergoes a single or a plurality of such reciprocal
reflections, then is output from the light output surface S.sub.0.
The light which is output in this manner is utilized as
illumination light Lr that illuminates regions comparatively far
from the optical axis C. W.sub.1 in FIG. 4 denotes the width of a
light emitting area based on light Lt, which is not reflected by
the semireflective surface S.sub.1 and is transmitted therethrough
(that is, W.sub.1 corresponds to the width of a light emitting area
of a conventional light diffusing element). W.sub.2 in FIG. 4
denotes the width of a light emitting area in the case that the
light Lr, which is output after being reflected by the
semireflective surface S.sub.1, is also included. As illustrated in
FIG. 4, propagation of light in directions away from the optical
axis C is promoted within the light diffusing element 33.
Therefore, W.sub.2 becomes greater than W.sub.1, and the light
emitting area of the secondary light source is enlarged.
Then, an image of a portion to be observed, which is illuminated by
the illumination light, is obtained by the CCD 30. The image
signals output from the CCD 30 undergoes various processes in the
analog processing circuit of the circuit board 31, then are input
to the DSP 43 of the processing apparatus 11 via the signal cables
32. The DSP 43 administers various signal processes onto the input
image signals, and generates image data. The generated image data
are displayed as an endoscope image on the monitor 20 via the D/A
converter 45.
In the case that treatment of a diseased site is necessary under
endoscope observation, the electric scalpel 36 is inserted into the
forceps channel 35 through the forceps opening 17. Then, the tip of
the electric scalpel 36, to which high frequency electric current
is applied, is caused to contact the diseased site to cut and
cauterize the diseased site.
As described above, the light diffusing element of the present
invention and the light guide for an endoscope equipped with the
light diffusing element have the semireflective surface that
reflects a portion of the light, provided to intersect with at
least the optical axis of the optical fiber. Thereby, propagation
of light in directions away from the optical axis of the optical
fiber can be promoted during the step of reflecting the portion of
the light that enters the light diffusing element. As a result, it
becomes possible for light to reach portions of the light diffusing
element away from the optical axis of the optical fiber, in the
light diffusing element and the light guide for an endoscope
equipped with the light diffusing element.
[Design Modifications to the Light Diffusing Element]
<First Design Modification>
In the description of the light diffusing element according to the
first embodiment and the light guide for an endoscope equipped with
the light diffusing element, the semireflective surface S.sub.1 was
formed by a semireflective film 38 provided on the light output
surface of the light diffusing element 33. However, the light
diffusing element and the light guide for an endoscope equipped
with the light diffusing element of the present invention are not
limited to such a configuration.
For example, the semireflective surface S.sub.1 may be designed to
be of a shape that protrudes rearward, as illustrated in FIGS. 5A
and 5E. A semireflective surface S.sub.1 having such a
configuration may be produced by molding the light transmitting
member 37 of the light diffusing element 33 such that the portion
thereof that intersects with the optical axis C is recessed, and by
forming the semireflective film 38 on the recessed portion 71.
FIG. 5A is a diagram that schematically illustrates the structure
of a light guide for an endoscope which is designed such that the
semireflective surface S.sub.1, which is formed as a curved
surface, protrudes rearward. Even if the light diffusing element 33
having this configuration is employed, a portion of the
illumination light L.sub.o that propagates through the light
diffusing element 33 is reflected in the rearward direction by the
semireflective surface S.sub.1 formed by the semireflective film
38. Ideally, the remainder of the light is transmitted through the
semireflective surface S.sup.1. The light which is transmitted
through the semireflective surface S.sub.1 is utilized as
illumination light Lt, which illuminates a region comparatively
close to the optical axis C. Meanwhile, the light which is
reflected rearward by the semireflective surface S.sub.1 is
reflected frontward by the totally reflective film 39, which is
coated on the side of the light diffusing element 33 toward a light
input surface thereof, then is output from the light diffusing
element 33. In the case that the semireflective surface S.sub.1 is
designed as a rearwardly protruding shape, it becomes possible for
the semireflective surface to intersect a plane perpendicular to
the optical axis C. This means that when a plane, which is a cross
section that includes the optical axis C, is considered, the
semireflective surface can be formed at an angle with respect to
the plane perpendicular to the optical axis C. In this case, light
which is reflected by the semireflective surface S.sub.1 is
reflected in directions at twice the angle compared to a case in
which light is reflected by a surface perpendicular to the optical
axis. Thereby, the light diffusing element illustrated in FIG. 5A
can promote propagation of light in directions further from the
optical axis of the optical fiber compared to the case illustrated
in FIG. 4. Further, by the effect of the aforementioned angle of
inclination, the diffusion angle .phi. of the light Lr which is
reflected rearward by the semireflective surface S.sub.1 then
output thereafter becomes greater than the diffusion angle .theta.
of the light Lt which is transmitted through the semireflective
surface S.sub.1. Thereby, the diffusion angle of light which is
output from the light diffusing element 33 is increased as a whole,
and it becomes possible to easily illuminate an even wider
region.
FIG. 5B is a diagram that schematically illustrates the structure
of a light guide for an endoscope which is designed such that a
semireflective surface S.sub.1 formed as a cone protrudes rearward.
Examples of conical shapes include circular cones and polygonal
cones, such as triangular cones. Forming the semireflective surface
S.sub.1 as a cone is advantageous in that the design for imparting
the semireflective surface with an angle with respect to a plane
perpendicular to the optical axis C is facilitated. Further, in the
case that the conical shape is a polygonal cone, the lateral
surfaces thereof can be set as appropriate in order to more
effectively promote propagation of light into predetermined
directions within the light diffusing element 33. Specifically,
FIG. 6A is a front view that schematically illustrates the
structure of the light diffusing element of FIG. 5B in the case
that the conical semireflective film is formed as a triangular
cone. In FIG. 6A, two of the three lateral surfaces of the
triangular cone are oriented so as to enable light to be reflected
in directions away from the optical axis of the optical fiber. The
orientations of the lateral surfaces are set as appropriate
according to the directions in which light is to be reflected. It
is not necessary for the axis of the conical shape of the
semireflective surface S.sub.1 and the optical axis of the optical
fiber 34 to be matched. The distribution of light energy can be set
as appropriate by shifting the axis of the conical shape of the
semireflective surface S.sub.1 and the optical axis of the optical
fiber 34, for example.
<Design Modification 2>
In the description of Design Modification 1, the light diffusing
element and the light guide for an endoscope equipped with the
light diffusing element were described as a case in which the
semireflective surface S.sub.1 was formed as a rearwardly
protruding shape. However, the light diffusing element and the
light guide for an endoscope equipped with the light diffusing
element of the present invention are not limited to such a
configuration.
For example, FIG. 6B is a diagram that schematically illustrates
the structure of a light guide for an endoscope which is designed
such that a semireflective surface formed as a cone protrudes
frontward. A semireflective surface S.sub.1 having such a
configuration may be produced by molding the light transmitting
member 37 of the light diffusing element 33 such that the portion
thereof that intersects with the optical axis C protrudes, and by
forming the semireflective film 38 on the protruding portion
72.
<Design Modification 3>
In the description of the light diffusing element according to the
first embodiment and the light guide for an endoscope equipped with
the light diffusing element, the semireflective surface S.sub.1 was
formed by a semireflective film 38. However, the light diffusing
element and the light guide for an endoscope equipped with the
light diffusing element of the present invention are not limited to
such a configuration.
For example, the semireflective surface S.sub.1 may be an interface
between materials having different refractive indices. Such a
structure can be produced by produced by molding the light
transmitting member 37 of the light diffusing element 33 such that
the portion thereof that intersects with the optical axis C is
recessed, and by filing the recessed portion with a material having
a refractive index less than that of the light transmitting member
37, as illustrated in FIG. 7A. Alternatively, an air gap may be
formed in the recessed portion, as illustrated in FIG. 7B. This
configuration yields the advantageous effect that the process of
forming the semireflective film can be omitted, resulting in the
light diffusing element being able to be produced at low cost.
Glass or an adhesive agent may be employed as the material having a
refractive index less than that of the light transmitting member
37. In addition, material 73 having a different refractive index or
an air gap 74 may be employed to form a second reflective surface
S.sub.2 that reflects a portion of the light reflected by the
semireflective surface S.sub.1, which is a first reflective
surface, frontward as illustrated in FIGS. 7C and 7D.
<Design Modification 4>
In the description of the light diffusing element according to the
first embodiment and the light guide for an endoscope equipped with
the light diffusing element, a case was described in which the
light transmitting member 37 is that in which fine scattering
particles are dispersed. However, the light diffusing element and
the light guide for an endoscope equipped with the light diffusing
element of the present invention are not limited to such a
configuration.
For example, a light transmitting member may be constituted by a
region 37a that includes fine scattering particles, and a region
37b that does not include fine scattering particles, as illustrated
in FIGS. 8A, 8B, and 8C. In this case, the light transmitting
member is designed such that light output from the optical fiber 34
passes through the region 37a at least once. FIG. 8A is a diagram
that illustrates the structure of a light diffusing element in
which the region 37a that includes the fine scattering particles is
provided toward the light input side of the light transmitting
member. Such a structure may be produced by coating the fine
scattering particles to form a scattering surface.
Note that when forming a scattering surface on the surface of the
light transmitting member, the scattering surface of the light
diffusing element is not limited to that which employs fine
scattering particles. The scattering surface may be formed by
polishing a surface of the light transmitting member with a lapping
sheet (for example, LFG1P by Thorlabs). As another example, the
scattering surface may be produced by forming a micro lens
array.
FIG. 8B is a diagram that illustrates the structure of a light
diffusing element in which the region 37a that includes the fine
scattering particles is provided toward the light output side of
the light transmitting member. In the case that the configuration
of FIG. 8B is adopted, no fine scattering particles are present
between the output end of the optical fiber 34 and the
semireflective surface S.sub.1. Therefore, control of the optical
paths of light reflected by the semireflective surface S.sub.1 is
facilitated. Accordingly, uniformization of the intensity of light
at the light output surface S.sub.0 of the light diffusing element
is facilitated. As another alternative, regions 37a that include
the fine scattering particles may be provided at portions of both
the light input side and the light output side of the light
transmitting member 37, as illustrated in FIG. 8C.
<Design Modification 5>
In the light diffusing element of the present invention and the
light guide for an endoscope equipped with the light diffusing
element, a light transmitting member 37c, in which the refractive
index becomes greater as the distance from the optical axis of the
optical fiber 34 increases, may be employed as illustrated in FIG.
9A. FIG. 9B is a graph that illustrates the distribution of
refractive indices within the light transmitting member 37c in the
y axis direction, using the optical axis as a reference along the y
axis. In the graph, n0 denotes the refractive index of the light
transmitting member 37a along the optical axis.
<Design Modification 6>
In the description of the light diffusing element according to the
first embodiment and the light guide for an endoscope equipped with
the light diffusing element, a case was described in which the
light diffusing element 33 and the optical fiber 34 are in close
contact. However, the light diffusing element and the light guide
for an endoscope equipped with the light diffusing element of the
present invention are not limited to such a configuration.
For example, the light diffusing element 33 and the optical fiber
34 may be separated from each other as illustrated in FIG. 10A.
Thereby, the size of the secondary light source formed on the light
diffusing element can be increased, and an advantageous effect that
the beam can be made more uniform can be obtained.
<Design Modification 7>
The light diffusing element of the present invention and the light
guide for an endoscope equipped with the light diffusing element
may employ an optical fiber 34 having a tapered portion 34a, as
illustrated in FIG. 10B. The tapered portion 34a is in the vicinity
of the output facet of the optical fiber 34 and is of a tapered
shape in which the core of the optical fiber becomes thinner toward
the output facet. Thereby, the diffusion angle of the light output
from the output end of the optical fiber 34 can be increased, and
an advantageous effect that light can be enabled to reach portions
of the light diffusing element farther from the optical axis of the
optical fiber is obtained.
<Design Modification 8>
In the description of the light diffusing element according to the
first embodiment and the light guide for an endoscope equipped with
the light diffusing element, the totally reflective film 39 was
employed to form a surface that reflects the light reflected by the
semireflective surface S.sub.1 frontward. However, the light
diffusing element and the light guide for an endoscope equipped
with the light diffusing element of the present invention are not
limited to such a configuration.
For example, the light diffusing element 33 constituted by the
light transmitting member 37 and the semireflective film 38 may be
fitted into a reflective member 75 that reflects the light
reflected by the semireflective surface S.sub.1 frontward, as
illustrated in FIG. 11. The reflective member 75 may be formed by a
metal material.
In addition, in the case that the light diffusing element 33 and
the optical fiber 34 are separated from each other as described
above and the reflective member 75 is appropriately designed, the
semireflective surface may be provided on the surface at the light
input side of the light diffusing element 33. Such a semireflective
surface may be produced by forming a metal film as the
semireflective film on the surface of the light diffusing element
33 at the light input side thereof.
* * * * *